/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.ofcoder.klein.consensus.facade;

import java.io.Serializable;

/**
 * consensus content.
 */
public interface Command extends Serializable {

    Command NOOP = new Command() {

        @Override
        public String getGroup() {
            return Noop.GROUP;
        }

        @Override
        public Object getData() {
            return Noop.DEFAULT;
        }
    };

    String getGroup();

    /**
     * client's input data.
     *
     * @return data
     */
    Object getData();

    /**
     * No operation proposal.
     */
    class Noop implements Serializable {
        public static final Noop DEFAULT = new Noop();
        public static final String GROUP = "NOOP";
    }
}
